In aged cats a series of interdisciplinary studies will be carried out with the objective of defining changes in sheep and wakefulness due to the aging process as revealed by correlated behavioral, electrophysiological and neuroanatomical techniques. The circadian distribution of a sleep and waking states and the attendent patterns of electroencephalographic, electroocular, electromyographic, cardiac and respiratory activity will be examined. These data will be individually analyzed and cross-correlated to generate a comprehensive behavioral and electrophysiological profile of state-dependent patterns of neural activity. Combined light (Golgi) and electron microscopic analysis of the neural substrates for the behavioral and electrophysiological data obtained during sleep and wakefulness will be carried out to provide a comprehensive description of the regulation of state-dependent processes in the aging feline brain. We have chosen to study the influence of age on central neural processes in cats in order to pursue a controlled, interdisciplinary experimental program that could not be realistically performed in humans. Additionally, in our preliminary studies, we found dramatic changes in sleep and wakefulness in aged cats. Since all neural and behavioral patterns of activity are carried out either during sleep or wakefulness, a detailed description of aging changes in these fundamental states, combined with functionally oriented neuroanatomical studies, was deemed an appropriate avenue to pursue in our initial interdisciplinary explorations of the aging process in the central nervous system.